Abstract
The far-infrared and low-frequency Raman spectra of 1,3-Dioxole have been analyzed. The gas-phase far-infrared spectrum shows a series of eleven singlequantum- jump and three triple-quantum-jump transitions in the 40-330 cm'1 region. The low-frequency Raman spectrum exhibits eight ring-puckering transitions corresponding to Av=2 or 4 transitions in the 160-300 cm'1 region. The ringpuckering potential energy function was determined to be V^cm'1) = 1.59 x10s x4 - 4.18 x 104 x2, where x is the ring puckering coordinate in A. This function indicates that the molecule is puckered with a barrier to planarity of 275 cm'1 and a bending angle of 24°. The unexpected non-planarity of 1,3-dioxole is attributed to the anomeric effect which can be present in molecules with O--C--O linkages. Molecular mechanics calculations utilizing the MM3 parameterization predict a planar structure for this molecule. However, the anomeric effect dictates that each of the =C--O--C--O torsional angles should have a strong tendency to increase from 0° towards 90° in order to optimize n-a* overlap. When the MM3 force field is modified to reflect this by increasing the magnitude of the two-fold torsional potential energy term V2 to -5.965 kcal/mole, a reasonably good agreement between the experimental and molecular mechanics potential functions can be obtained. The gas-, liquid-, and solid-phase mid-infrared and Raman spectra of 1,3- dioxole have also been analyzed. A satisfactory vibrational assignment of the twenty-one fundamental vibrations has been achieved. The low-frequency far-infrared spectra of 1,3-dioxolane and 1,3-dithiolane have been examined. It was concluded that 1,3-dioxolane is a nearly free pseudorotor with a pseudorotational barrier which is less than 50 cm'1 while 1,3- dithiolane exhibits hindered pseudorotation with a moderate barrier to pseudorotation. Ethyl nitrite-d0 and -d5 have been synthesized. Band contour simulations of the N = 0 stretching bands observed in the gas-phase mid-infrared spectra of the deuterated species indicate that the Q branch at 1670.5 cm'1 can be ascribed to the tram,gauche rotational isomer. The band at 1611.5 cm 1, on the other hand, may result from the superposition of two conformers.
Cortez, Enriqueta (1994). Conformational analysis of 1,3-Dioxole, 1,3-dioxolane, 1,3-dithiolane, and ehtyl nitrite. Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -1550459.